1. Field of the Invention
The present invention relates to a positive resist composition sensitive to far ultraviolet ray, which is used for fine processing of a semiconductor device or the like. More specifically, the present invention relates to a positive resist composition for exposure with electron beam, X-ray or EUV.
2. Background Art
The integration degree of integrated circuits is recently becoming higher and higher and in the production of a semiconductor substrate such as VLSI, an ultrafine pattern having a line width of half-micron or less is demanded.
Non-Patent Document 1: Proc. SPIE, Vol. 2483, page 53 (1995) discloses a positive resist composition containing a copolymer of hydroxystyrene and tert-butyl acrylate, and Patent Documents 1 to 3: JP-A-10-53621 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-2002-323768 and JP-A-2003-177537 disclose a positive resist composition containing an acid-decomposable polyhydroxystyrene. Patent Document 4: JP-A-2003-322970 discloses a resist comprising a copolymer containing α-hydroxyacrylate-based monomer and hydroxystyrene.
However, along with the requirement for enhanced performance, these resists comprising a resin having an aromatic ring suitable for lithography by electron beam or the like, such as styrene skeleton, are demanded to be more improved, for example, in the sensitivity, resolution, pattern profile and line edge roughness.